The subject matter of the present invention relates to a firing head adapted for use in a perforating gun, and more particularly, to a firing head and perforating gun connected to a coiled tubing which may be disposed within a tubing string in a wellbore and is adapted to move freely within the tubing string, the firing head detonating a booster of a detonating cord and initiating the propagation of a detonation wave in the detonating cord in response to a fluid pressure disposed within the coiled tubing, the detonation wave detonating the perforating gun.
The use of coiled tubing in oil well related operations is increasing in popularity. The reason is relatively simple. Instead of lowering wellbore equipment into a wellbore as part of a tubing string, a much more economical alternative approach involves the lowering of the wellbore equipment into the tubing string itself on the end of a coiled tubing. It is much more expensive to remove a tubing string from a wellbore than it is to remove a coiled tubing from a tubing string. A perforating gun is one example of such wellbore equipment. The perforating gun includes a firing head for detonating the perforating gun and perforating a formation traversed by the wellbore. Since the aforementioned alternative approach is preferred, a new firing head adapted for use in a perforating gun is needed, one which can be connected to a coiled tubing on one end and to the perforating gun on the other end, one which is sized and shaped to allow the firing head and perforating gun to move freely within the tubing string, and one which can can be detonated in response to a fluid pressure in the coiled tubing. In addition, since many common oil field operations require circulation of wellbore fluids or pumping fluids into the formation, the new firing head should include a circulating feature for enabling fluids in an annulus defined by the tubing string or the wellbore to circulate through the firing head and into the coiled tubing, or for enabling fluids in the coiled tubing to circulate from the coiled tubing to the annulus, the circulation taking place before and/or after the perforating gun perforates the formation.